1. Field of the Invention
This invention relates to vacuum assisted evaporative drying systems, and more specifically to clothing drying systems using latent heat recovery to improve energy efficiency.
2. Previous Art
Systems used for drying articles, such as the typical home clothes drier, use large amounts of energy. Most home dryers tumble damp clothing in a tumbler. The dryer also heats air and continually pumps hot air, at atmospheric pressure, through the damp clothing. The clothing dries. The hot air continually exhausts from the drier into the atmosphere. The exhausted heat is not recovered. Energy is wasted.
A number of attempts to conserve energy by reducing the drying time have been made. For example, some dryers rely on reduced pressures to dry clothing. See for example U.S. Pat. Nos. 4,615,125, 4,250,628, 4,057,628, 3,308,553, 3,229,382 and 3,030,712. At reduced pressure, energy is saved in two ways. Firstly, heating air at reduced pressures requires less energy. Secondly, evaporation occurs more rapidly at reduced pressures. With reduced pressures, the drying cycle shortens and energy is used for a shorter period of time. Also, at the lower temperature and shorter cycle, the clothing is subjected to less wear and less heat induced damage.
Various dryers recapture heat. U.S. Pat. No. 4,447,965 to Bray, teaches recirculation of heated air through the dryer. A compressor and electrical heating element raise the temperature of the recirculated air. Latent heat is recovered at a heat pump condenser via drying fluid which enters the drying chamber.
U.S. Pat. No. 5,13 1,169 to Jaster teaches how to move heated air through a tumbler operated at a sub-atmospheric pressure. Air is exhausted. The exhausted air passes through a heat exchanger so that heat is recaptured. The amount of energy needed to dry clothing is reduced. Jaster does not teach the use of a condensation chamber.
What is needed is a drier which more efficiently dries clothing by combining the advantages of reduced pressure with the advantages heat recapturing.